The application is a continuation-in-part of U.S. application Ser. No. 09/438,814, filed Nov. 10, 1999 now U.S. Pat. No. 6,232,926.
This application claims benefit under 35 U.S.C. xc2xa7 119(e) of a U.S. provisional application of Anh Nguyen et al entitledxe2x80x9cMultiple-Coupling Vehicle SDARS Glass Mount Antenna Systemxe2x80x9d, Ser. No. 60/200,463, filed Apr. 28, 2000, the entire content of which is incorporated herein by reference.
The invention relates generally to transmission of radio frequency signals (e.g., SDARS signals) from an antenna across a dielectric such as glass to a receiver disposed in a vehicle, as well as the transmission across glass of power from the receiver to antenna electronics. The invention also relates to an integral antenna assembly for mounting externally on the dielectric surface that comprises one or more antennas, antenna electronics, as well as components for radio frequency and direct current coupling through the dielectric with internally mounted receiver components.
With reference to FIG. 1, a number of antenna systems have been proposed which provide for the transfer of radio frequency (RF) energy through glass or other dielectric surface to avoid having to drill holes, for example, through the windshield or window of an automobile for installation. Glass-mount antenna systems are advantageous because they obviate the necessity of having to provide a proper seal around an installation hole or other window opening in order to protect the interior of the vehicle and its occupants from exposure to external weather conditions.
In the conventional antenna system 20 depicted in FIG. 1, RF signals from an antenna 22 are conducted across a glass surface 24 via a coupling device 26 that typically employs capacitive coupling, slot coupling or aperture coupling. The portion of the coupling device 26 on the interior of the vehicle is connected to a matching circuit 28 which provides the RF signals to a low noise amplifier (LNA) 32 at the input of a receiver 34 via an RF or coaxial cable 30. The antenna system 20 is disadvantageous because the matching circuit 28, losses associated with the cable 30 and RF coupling (e.g., on the order of 2 to 4 dB or more) cause an increase in system noise.
Another proposed antenna system 40, which is described with reference to FIG. 2, has an RF coupling device similar to that used in the antenna system 20 depicted in FIG. 1, as well as DC coupling components to provide power to the antenna electronic circuitry. The antenna system 40 is configured to transmit video signals from satellite antenna electronics through a glass window 46 into a structure such as a residence or office building without requiring a hole through the glass. An exterior module 42 is mounted, for example, on the exterior of the structure, while an interior module 44 and receiver 48 are provided within the structure. RF coupling units 50a and 50b are provided on opposite sides of the glass 46 which is typically a window in the building. RF coupling unit 50b is connected to the exterior module 42 via a coaxial cable 54 to allow the exterior module 42 to be located remotely (e.g., on the building rooftop) therefrom. The exterior module 42 encloses an antenna 52 and associated electronics (e.g., an LNA 56) to receive RF signals, which are then provided from the LNA 56 to the coupling device 50b via the cable 54 for transfer through the glass 46.
With continued reference to FIG. 2, RF energy transferred through the glass 46 is processed via a matching circuit 58. The matching circuit 58 is connected to a receiver 48 by another coaxial cable 60. In addition, DC power is provided from the interior module 44 to the exterior module 42 (e.g., to provide power for the LNA 48) by low frequency DC coupling coils 62a and 62b mounted opposite each other on either side of the glass 46. In a conventional satellite TV system, electrical power for the satellite antenna electronics is provided from the receiver 48 on the same coaxial cable that provides video signals from the antenna 52 to the receiver 48.
While the provision of DC power to antenna electronics is useful, the matching circuit and cable losses associated with the antenna system 40 are not desirable for such applications as an in Satellite Digital Audio Radio Services (SDARS) system antenna for a vehicle. At 800 MHz, the coupling loss experienced with conventional glass mount antenna arrangements can be as much as 3 dB. At higher frequencies, the coupling loss increases substantially. For such high frequency applications as satellite radio operating at 2.4 GHz, the coupling loss is expected to be unacceptably high (e.g., 2 to 4 dB), making reception difficult. A need therefore exists for a glass-mounted antenna arrangement for high frequency wireless communication applications, and particularly, satellite radio applications, that reduces coupling loss.
Further, installation of a cable (e.g., such as the coaxial cable 54 in FIG. 3) on the exterior of a vehicle window or windshield is undesirable in terms of installation, as is drilling through glass. The installation of an antenna assembly 42 located remotely with respect to the external coupling devices indicated at 45 is generally considered unattractive to consumers of mobile satellite services. A need therefore exists for a vehicle antenna mounting system whereby the antenna, associated antenna electronics (e.g., LNA) and RF and DC coupling are provided in an integral assembly for installation on the exterior of a vehicle.
The above described disadvantages are overcome and a number of advantages are realized by a vehicle antenna mounting system whereby the antenna, associated antenna electronics (e.g., LNA) and RF and DC coupling are provided in an integral antenna assembly for installation on the exterior of a vehicle.
In accordance with an aspect of the present invention, the integral antenna assembly comprises a base section enclosing the associated antenna electronics and RF and DC coupling devices, and an antenna section pivotably mounted on the base section comprising the antenna.
In accordance with another aspect of the present invention, the vehicle antenna mounting system comprises two or more antennas in the integral antenna assembly for SDARS reception on at least one satellite channel and a terrestrial channel. In addition another satellite channel can be provided for diversity purposes, or a global positioning system (GPS) satellite receiver for performing location services, among others, for the vehicle.
In accordance with still yet another aspect of the present invention, the antenna section comprises a quadrifilar antenna for reception of one or more satellite channels, and a linear antenna disposed within the quadrifilar antenna for reception of terrestrial signals.